If it uses a XR-E then you’ll need a new mcpcb to use the newer 3535 leds. Preferable a copper one.
The manual for the M20 I found on google said 250 lumens max for the R2. That means the driver is only putting out to the led some where in the range of 750ma. The XR-E R2 should put out about 120 lumens per 350ma.
If you prefer long run times this driver will give it but at a cost of lumens. Changing just the led out to a LH351D in a good bin should give you around 400 lumens.
Thats a good increase from the original XR-E. It all depends on how many lumens you want and if you had rather have high lumens or long run times.
If 400 lumens in high is acceptable then just change the mcpcb and led to a LH351D. At this low of current a aluminum mcpcb should work fine.
They are a medium floody. they will be alot more flooder than the tiny XR-E. You could ask Richard to slice the LH351D dome. This will tighten the beam up considerably.
Keep in mind that the XR-E in its day was the thrower led. If you are looking to get something around the same amount of throw then a different led will work better but again at a loss of lumens. To out perform the original you need another driver if throw is what your after.
This is probably the best equivalent to the XR-E. LED test / review - OSRAM OSLON Black Flat HWQP - still highest luminance of all LEDs to date!
Umm, a “metal ring around the LED” sounds like an old old old XR-E. Bigger hole, like for a 5050/XM (maybe).
Same E chip as in XP-Es, but ironically the XR package has a bit better power handling.
You could try any LED like the ’351 and see if a gasket is enough to center it (or any non-XR-E LED). Else, you might need a shim/spacer, and/or find some way of lowering the reflector flush over the chip, else the focus might be “off” (doughnut-beam, rings, etc.).
On the bright (haha) side, the bigger hole might be enough to stick an XHP in there. Or an MT-G2 (yummy!). But then for sure you’d need a different driver, as they’re not “3V” LEDs anymore, but “6V” and “12V” and such.
Well you know how it goes, It’s easy to get spoiled by lots of lumens. I’ve gotten accustomed to my Zebralight SC62w that goes everywhere with me. But I know that less lumens can give as good as or better throw than more lumens depending on the matching of the reflector. 400 lumens isn’t too bad as an upgrade. Will just have to see how it behaves with the currant reflector.
Actually, before you go crazy with anything, you want a thrower or a flooder?
Honestly, for throw, get a different light that could handle more power (ahr! ahr! ahr!).
With a ’351, it’d make a quite nice all-arounder. Even better if you’d “need” diffusion film to smooth out an ugly beam.
I’ve got a few LuxPro lights that use XP-G3s which produce truly ugly-ass beams, and with diffusion film, they’re beautiful. Floody, one big blanket of light instead of hotspot+spill, but really handy close-in.
For throw, I got dedicated throwers for that.
200lemons ain’t gonna throw very far, even in a pencil beam. I got an XP-E2 in a C8 host that throws a nice tight disc of light, but it’s maybe 300lm, and that’s not stressing it out much, by design. I could push it quite a bit more, but chose not to. That throwy, though, and it’s a one-trick pony. Kinda useless for close-in snooping, unless you want to look down drainage pipes or something.
Its really hard to say how it will do with a 3535 led. I have seen them in other lights have a bigger hotspot but alot more lumens makes up for it down range.
But I have also seen it not throw as far and become more floody that wasn’t really usable. It depends alot on the reflector I guess.
I upgraded a HS-802 to a dedomed xpl and liked it better than the XR-E but the current was increased. The xpl should be making around 1200 lumens. hs-802 Pill? - #8 by moderator007
Yeah antique-ish. And yeah, I guess that’s the modding part. 
Maybe I’ll work up to modding slowlier since I’m not as sharp as you guys. 
Yeah, like trying to throw normal 12V car parts in an old antique car with a 6V system…
Just need an all-arounder (and a project). Will probably be a spare truck light. I’ve got some (somewhat) throwers.
Been there and done that too. Hoping for a more fun project.
I guess I’ll do the Thomas Edison thing and try it. Hopefully it won’t take as many tries. 
With these older drivers it is possible the current might be increased some just by changing the sense resistor. Its usually a easy mod if you have a soldering iron.
If you can get the driver out with out to much trouble and take a good close up pic, we might be able to help with that. Just depends on what Olight used for regulation.
If you want throw go with a sst-20.
two wire emitter swaps take old to a new level and the ability to look at a new tint.
Is the reflector smooth or orange peel ?
If you can't get a decent beam .Dc-fix will soften the blow .
If it's an olight I'd consider changing the glass to non coated clear glass .none of it overly complicated and like you said ... could it get any worse ?
The driver is on the bench so I’ll try to get a pic tomorrow.
Hmmm. sst-20 you say. My FW3A is coming in sst-20. The reflector is OP. Something else to think about. Was planning to replace or scrub the glass. I have put sapphire glass before in when I can.
Ok. So I have a couple really nice pictures of the M20 driver I took with my S 9 phone that I can't figure out how to upload to this thread. I'll keep working on it. In the meantime I think I might get several LEDs on boards and try them out.
Here’s a guide that might help.
Ok. Here’s one photo of the driver.
On the very bottom where the black wire is, there are two resistors connected to that solder blob or it looks like there in parallel with each other.
The very bottom one reads R20 it looks like. The top one I can’t really tell. Could you possible take a clear pic of that area or check with a DMM and see if they are in parallel and also read the value of the both resistors. Looks like those two are sense resistors and lowering the value can up the output current but I need to see what they are and if they are in parallel.
Both are R20. I’ll put a meter on it tomorrow if I get a chance.